語音降階
From Phonology
在語音學上，語音降階(downstep-phonetics)用以表示在聲調語言之音節與字詞之間，其聲調上之音位、或語音的"向下轉移"之特性。西非的語言上語音降階是廣為人所知曉的，但是日語(一種非聲調的語言)的音調重音現象是非常類似於非洲語言裡的語音降階特性。語音降階是對比於一般比較少出現的語音升階之語音特徵。在國際音標裡"語音降階"的符號是用一個上標的向下指箭頭來表示，不過目前Unicode還沒有支援這種符號。一般我們可以看到是用一個上標的感嘆號 ! 來替代它。
語音降階可以出現在有相同音位聲調的序列之間。舉例來說，當兩個中階的聲調出現在一塊時，比如在加納的多威語，第二個調子比起第一個調子來得低。因此，"向下轉移"的特性在下降階浮動與聲調台階扮演很重要的角色。
Phonemic downstep may occur when a low tone is 語音省略, or occurs as a 浮動聲調, and leaves a following tone at a lower level than it would otherwise be. 班巴拉語裡有一個例子出現。在這個語言裡，定冠詞是以一種浮動的低聲調型態來表現。With a noun in isolation, it docks to the preceding vowel, turning a high tone into a falling tone: [bá] river; [bâ] the river. However, when it occurs between two high tones, it downsteps the following tone: [bá tɛ́] it's not a river; [bá ↓ tɛ́] it's not the river.
Japanese pitch accent is similar. About 80% of Japanese words have an evenly rising pitch, something like French, which carries over onto following unstressed grammatical particles. However, a word may have a drop in pitch between 莫拉, or before the grammatical particle. 範例如下：
| /ka↓ki/ | /kaki↓/ | /kaki/ |
| [kákì] | [kàkí] | [kàkí] |
| 牡蠣 | 籬笆 | 柿子 |
In isolation like this, the first word has a high-low pitch, whereas the second and third are homonyms with a low-high pitch. 然而，當後接所謂"主語性"的不變詞 ga:，以致造成所有三個語詞是不相同的。
| /ka↓kiga/ | /kaki↓ga/ | /kakiga/ |
| [kákìgà] | [kàkígà] | [kàkīgá] |
| 牡蠣 | 籬笆 | 柿子 |
